State troopers say they're wary of certain motorcyclists that ride together in groups, known to endanger themselves and others. NBC's Stephanie Gosk reports

By Tom Winter, Lisa Riordan Seville and Andrew Blankstein, NBC News

A new and dangerous breed of motorcycle gang is popping up around the country, say authorities, as packs of young bikers on high-speed “crotch rockets” barrel down crowded highways performing stunts, weaving through traffic and taunting police, all for a few minutes of Internet glory.

These “crotch rocket” gangs film their exploits, which can include altercations with motorists and the law, and then post videos on YouTube. Police in New York City have arrested several men after video surfaced on the Web of a Sunday incident in which bikers surrounded and beat an SUV driver in Manhattan. The bikers had been taking part in an underground event called Hollywood Stuntz, in which bikers assembled en masse on city streets to perform wheelies and other stunts.

And police say they have trouble stopping the bikers, because their machines are so fast and maneuverable that it’s unsafe to chase them through traffic.

Sgt. Brian Brophy of the New York State Police said that officers will stop pursuits of fast bikes when it’s judged too dangerous. “As a trooper you end up terminating these pursuits a lot yourself, for the safety of the public, yourself and the biker,” he said.

“You can’t chase them because they’re crazy,” said former New York and Los Angeles chief of police Bill Bratton, now an NBC News analyst. “They endanger themselves and others.”

The packs have grown as motorcycle registrations have risen – 30 percent between 1990 and 2008 – and as new, high-performance machines that make tricks easier to perform have become available. But these packs, which sometimes come together based on little more than a Tweet or a Facebook post, are not true bike gangs in the old-school sense of the word, explains a federal law enforcement agent. They’re not rooted in neighborhoods, involved in dealing drugs or engaged in long-running feuds with other gangs, like the traditional groups that law enforcement refer to as Outlaw Motorcycle Gangs or OMGs.

The “OMGs” are usually white and sometimes use violence, including shooting or stabbing, to further their cause, explained the law enforcement official. He said that the sport bike crowd skews younger, is loosely affiliated and is racially diverse.

While these free-form, instant gangs may not be predisposed to violence, he said, a “mob mentality” can take over if they feel threatened, as happened in New York.

Mostly, what they want to do is tricks. “They are daredevil types into high-performance bikes,” he said, “a younger generation into the rush of high speeds and splitting lanes.”

And they want to do their tricks on public highways, with cameras rolling. Combine social media, YouTube and cheap, versatile handheld cameras, and you have a recipe for packs of bikers to assemble quickly, take over public streets and put the results on the Web for the world to see.

In other videos, bikers pop wheelies and dodge a police roadblock in Missouri:

Evade a roadblock on a California bridge:

And taunt police in Texas:

Dennis Cardwell, who started a mass ride in Missouri called Ride of the Century several years ago, says he’s no longer associated with the ride, in part because the numbers and behavior spiraled out of control.

The yearly event now draws as many as 2,000 riders. “We never thought it would get to the size that it has,” said Cardwell, 35, who no longer rides. “All of us would be scared on the highway with these large groups. A lot of it was younger kids who were newly into bikes and willing to take any risks, including popping wheelies at high speeds.”

Cardwell blames improved bikes and improved cameras for the spike in stunt videos on the Web, saying “technology is really the main culprit.”

“Now you’ve got camera phones, video phones,” he said. “You can post in seconds. That was what started the whole craziness of it all.”

Kevin Marino of Akron, Ohio, who started a stunt-riding group in the 1990s and runs a website called Starboyz where bikers post videos, also says that the rides and videos are trending upward -- and that the rides are becoming dangerous.

“There are rides where there are thousands of people. … Now there are so many bikes, bikes are hitting each other,” Marino said.

Like Cardwell, he said that technology had made the boom possible, making tricks easier and cameras more accessible – but he made particular note of GoPro cameras, which can be mounted on helmets.

“Everybody wants to be a movie star,” he said. “The GoPros are crazy. You’ll go on these street rides with 500 people and half the people will have GoPros.”

In New York City over the weekend, one of the members of a pack of motorcyclists driving up the Henry Hudson Parkway in Manhattan used a GoPro camera to capture an altercation between the bikers and the driver of a Range Rover. When a biker slowed in front of the SUV, the vehicle hit the bike. The vehicle then stopped, and the motorcyclists surrounded it.

YouTube

Christopher Cruz slows his motorcycle down in front of a Range Rover on Mahattan's West Side Highway on Sunday, Sept. 29, in this image from a video posted on YouTube.

Apparently believing he was in danger, the driver, Alexian Lien, then sped away, seriously injuring motorcyclist Edwin Mieses. Mieses is now in a New York hospital with internal injuries, crushed legs and possible paralysis. The bikers chased Lien up the highway and to an intersection, where, as his wife and daughter watched, he was pulled from the car and beaten. Police have arrested 28-year-old Christopher Cruz, the individual who allegedly slowed his bike in front of the SUV, and charged him with reckless driving and unlawful imprisonment. A second man was arrested and then released. Another suspect was expected to surrender.

The bikers had assembled for an informal event called Hollywood Stuntz that drew a swarm of motorcyclists from around the region. The NYPD said it was aware that the bikers were coming and had concentrated on steering them away from Times Square. Even before the Range Rover assault, 15 bikers were arrested, 68 summonses were issued and 55 bikes were seized.

Fellow rider Kevin Marino defended the motorcyclists. He said that although the violence against the driver was “obviously wrong,” the bikers were not acting as a gang and were reacting to an injury. “Half those guys probably didn’t know each other,” he said. “Someone just got run over. They went to see how he was doing.”

Dennis Cardwell said the incident “made me sick to my stomach,” and that he understood the SUV driver’s fear. “I would have panicked too, especially if I had my wife and kid in the car."

"Now I have three kids, I understand what it’s like to be on the highway to be in a car with my kids and my family,” said Cardwell. “You understand why people were mad at you when you were young.”